Editorial Type:
Article Category: Research Article
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Online Publication Date: 01 Jan 2017

Experimental Investigations on Rubber Friction Coefficient Dependence on Visco-Elastic Characteristics, Track Roughness, Contact Force, and Slide Velocity

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Page Range: 3 – 24
DOI: 10.2346/tire.17.450101
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ABSTRACT

The results of an experimental activity, carried out using a prototype of pin on disk machine and aimed at investigating the frictional behavior of visco-elastic materials in sliding contact with rigid asperities, are presented.

The pin is a rubber specimen coming from three different passenger automotive tires, while the disk is covered with glass, marble, or 3M anti-slip tape surfaces. Tests, performed both in dry and wet conditions, highlighted that the friction coefficient is strongly influenced by the effect that surface roughness plays on friction mechanisms of adhesion and hysteresis. The results confirmed the theoretical dependence of friction on vertical load, sliding velocity, rubber characteristics, and track conditions.

Keywords: friction mechanisms; tire friction test methods; adhesion; hysteresis; visco-elasticity; surface roughness
FIG. 1
FIG. 1

Rubber dynamic characteristics.

FIG. 2
FIG. 2

Test machine.

FIG. 3
FIG. 3

Specimens contact patches stamped on graph paper.

FIG. 4
FIG. 4

Specimen contact deformation during a test on marble.

FIG. 5
FIG. 5

Step test on dry glass (vertical load Fz = 50 N, relative speed Vs = 1.0 m/s).

FIG. 6
FIG. 6

Storage modulus for compounds C1, C2, and C3 (f = 1 Hz; displacement = 0.050 mm).

FIG. 7
FIG. 7

Tan δ for compounds C1, C2, and C3 (f = 1 Hz; displacement = 0.050 mm).

FIG. 8
FIG. 8

Linear 3M paper laser scan (Ra = 72 μm, λ ≈ 2 mm).

FIG. 9
FIG. 9

Repeatability analysis for compound C1, three dry surfaces, Fz = 20 N, ambient temperature. Each testing condition was repeated about 10 times. The error bars highlight standard deviations, always less than 2% of the measurement's average value, depicted by the central marker.

FIG. 10
FIG. 10

Friction coefficient vs load for the three compounds on dry glass (Vs = 1 m/s, ambient temperature).

FIG. 11
FIG. 11

Friction coefficient vs load for compound C1 on glass, marble, and 3M paper in dry and wet conditions (Vs = 1 m/s, ambient temperature).

FIG. 12
FIG. 12

Friction coefficient vs sliding velocity (step tests) for C1 compound on glass, marble, and 3M paper in dry and wet conditions (Fz = 20 N, ambient temperature).

FIG. 13
FIG. 13

Friction coefficient vs sliding velocity (step tests) for the compounds C1 and C3 on glass in dry and wet conditions (Fz = 20 N).

FIG. 14
FIG. 14

Storage modulus E′ for compounds C1 and C3.

FIG. 15
FIG. 15

Friction coefficient vs sliding velocity (step tests) for C1 and C3 compounds on 3M tape in dry and wet conditions (Fz = 20 N).

FIG. 16
FIG. 16

Tan δ curves for compounds C1 and C3 (enlargement of Fig. 6).

FIG. 17
FIG. 17

Friction coefficient vs sliding velocity (step tests) for C1 and C3 compounds on marble in dry and wet conditions (Fz = 20 N).

Contributor Notes

1 Corresponding author. Department of Industrial Engineering, University of Naples “Federico II,” Via Claudio 21, 80125 Naples, Italy. Email: flavio.farroni@unina.it
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